Have to add my two cents, since this is now happening in my game. It has often occurred with the desk chair that comes with the More Views video station, and so far it also has occurred with the Captain Rodrigo de Pablo couch - which it never has before. If it occurs with anything else, I'll be sure to update!
My sim was complaining the chair was uncomfortable on a chair with a comfort level of 10. That makes no sense to me. Chairs don't get any more comfortable! I admit, it was a dining room chair, but still, it says comfort level 10. That should count for something.
The Model L337 desk chair that came with GL, I believe, is also giving the uncomfortable moodlet. I'll continue to post any new ones I find.
